Surfactant protein C gene (SFTPC) variations may cause hereditary interstitial lung disease (HILD), a disease with variable prognosis. The evaluation of treatment responsiveness of HILD with SFTPC variation remains unclear. We present the case of a child with HILD whose respiratory condition was appropriately evaluated using a high-flow nasal cannula (HFNC). A 12-month-old boy with SFTPC variation developed progressive respiratory failure. Although he was once considered a candidate for lung transplantation, his respiratory condition was improved by hydroxychloroquine treatment, which prevented further therapy. Compared to a conventional nasal cannula, which could not deliver a stable oxygen concentration, HFNC allowed us to evaluate the improvement of oxygenation more accurately.